Reactivity in Chemistry
Fatty Acid Synthesis
FA4. Solutions to Selected Problems
The product becomes conjugated. In general, the more conjugation there is in the product of an aldol addition, the more likely is a subsequent condensation (elimination or dehydration). However, other conditions can lead to the loss of water.
Entropy. The dehydration or elimination takes one molecule (the beta-hydroxy thioester) and converts it into two molecules (the water and the alpha,beta-unsaturated thioester. That change represents an increase in internal entropy. Because the entropy term in free energy is weighted by temperature (ΔG = ΔH - TΔS), it predominates as the temperature rises.
In the case of the malonyl enolate, there is additional delocalisation as demonstrated by resonance. This anion has extra stability.
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